| 1. |
- Fu, Le, et al.
(author)
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Enhanced Bacteriostatic Properties of Ti Alloys by Surface Nitriding
- 2023
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In: Biomedical Materials & Devices. - : Springer Nature. - 2731-4812 .- 2731-4820. ; 1, s. 760-771
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Journal article (peer-reviewed)abstract
- Surface nitriding has been widely used to improve the surface physicochemical properties of Ti alloys. However, the currently utilized surface nitriding methods, such as laser nitriding, typically require expensive and complicated instruments, which makes surface nitriding a less cost-effective process. Meanwhile, the antibacterial properties of surface-nitrided Ti alloy implants have not been evaluated. Thereafter, in this study, we were aiming to develop an effective, simple, and cost-effective surface nitriding strategy to enhance the antimicrobial properties of Ti alloy implants. The surface nitriding strategy was realized by wet-chemical etching and thermal treatment at controlled conditions. Results showed that the above surface modification treatments exerted significant effects on the phase composition and morphology of the newly formed phases on the surface of Ti samples. Crystalline TiN and TiO2 formed after treatments. Meanwhile, amorphous nitrides and oxynitride were also presented on the sample surfaces. The surface-modified Ti samples showed a bacterial inhibition effect compared with the non-treated Ti ones, and the bacterial inhibition effect was attributed to the released ammonia species from the surface of Ti samples. The surface modification strategy shows promise to improve the bacteriostatic property of Ti implants in dental and orthopedic fields.
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| 2. |
- Fu, Le, et al.
(author)
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Far from equilibrium ultrafast high-temperature sintering of ZrO2-SiO2 nanocrystalline glass-ceramics
- 2023
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In: Journal of The American Ceramic Society. - : John Wiley & Sons. - 0002-7820 .- 1551-2916. ; 106:7, s. 4005-4012
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Journal article (peer-reviewed)abstract
- Ultrafast high-temperature sintering (UHS) is a novel sintering technique with ultrashort firing cycles (e.g., a few tens of seconds). The feasibility of UHS has been validated on several ceramics and metals; however, its potential in consolidating glass-ceramics has not yet been demonstrated. In this work, an optimized carbon-free UHS was utilized to prepare ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs). The phase composition, grain size, densification behavior, and microstructures of NCGCs prepared by UHS were investigated and compared with those of samples sintered by pressureless sintering. Results showed that NCGCs with a high relative density (similar to 95%) can be obtained within similar to 50 s discharge time by UHS. The UHS processing not only hindered the formation of ZrSiO4 and cristobalite but also enhanced the stabilization of t-ZrO2. Meanwhile, owing to the ultrashort firing cycles, the UHS technology allowed the NCGCs to be consolidated in a far from equilibrium state. The NCGCs showed a microstructure of spherical monocrystalline ZrO2 nanocrystallites embedded in an amorphous SiO2 matrix.
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| 3. |
- Fu, Le, et al.
(author)
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Liquid-phase sintering of ZrO2-based nanocrystalline glass-ceramics achieved by multielement co-doping
- 2023
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In: Journal of The American Ceramic Society. - : John Wiley & Sons. - 0002-7820 .- 1551-2916. ; 106:4, s. 2702-2715
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Journal article (peer-reviewed)abstract
- Liquid-phase sintering (LPS) is an effective pathway to assist the densification of ceramics. However, it has seldom been used to densify glass-ceramics. In the present study, a multielement co-doping strategy has been utilized to achieve LPS of a ZrO2-SiO2 nanocrystalline glass-ceramic. Compared with undoped samples densified by solid-state sintering, doping of equimolar Al, Y, and Ca promoted the densification of the glass-ceramic at lower temperatures with a faster densification rate. Ternary doping enhanced coarsening of ZrO2 nanocrystallites during sintering and annealing. The distribution of dopants was carefully observed with X-ray energy-dispersive spectrometry technique in scanning electron transmission microscopy mode. Results showed that the three dopants showed different distribution behaviors. After sintering, Y dopants were predominately distributed in ZrO2 nanocrystallites, whereas parts of Al and Ca dopants were distributed in ZrO2 nanocrystallites and part of them co-segregated at the ZrO2/SiO2 heterointerfaces. Meanwhile, the segregation of Ca dopant at some intergranular films among ZrO2 nanocrystallites was observed. Redistribution of dopants did not occur during annealing.
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| 4. |
- Fu, Le, et al.
(author)
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Microstructure of rapidly-quenched ZrO2-SiO2 glass-ceramics fabricated by container-less aerodynamic levitation technology
- 2023
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In: Journal of The American Ceramic Society. - : John Wiley & Sons. - 0002-7820 .- 1551-2916. ; 106:4, s. 2635-2651
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Journal article (peer-reviewed)abstract
- In this work, an aerodynamic levitation technology (ALT) was utilized to prepare ZrO2-SiO2 glass-ceramics with two different ZrO2 contents, that is, 35 mol% and 50 mol%. The glass-ceramics were partially melted at similar to 2000 degrees C or fully melted at similar to 3000 degrees C by ALT, followed by rapid quenching to obtain spherical glass-ceramic beads. The phase compositions and microstructures of the glass-ceramics were characterized. Crystallization of ZrO2 occurred during the solidification process and ZrO2 content, processing temperature, and the addition of yttrium (3 mol%) affected the crystalline phase of ZrO2. No ZrSiO4 or crystalline SiO2 were formed during the solidification process and the glass-ceramics were away from thermodynamic equilibrium due to rapid quenching. The glass-ceramics showed a microstructure of irregular-shaped ZrO2 micro-aggregates embedded in an amorphous SiO2 matrix, with lamellar twins and lattice defects formed within ZrO2 crystals. For samples prepared at similar to 3000 degrees C, a liquid-liquid phase separation occurred in the melt, which eventually resulted in the formation of large and irregular-shaped ZrO2 aggregates. In comparison, for samples prepared at similar to 2000 degrees C, pre-existed ZrO2 crystals formed during heating acted as nucleation sites during the cooling process, followed by grain growth to form large ZrO2 aggregates. Solidification and microstructure formation mechanisms were proposed to elucidate the solidification process during rapid cooling and the microstructure of the glass-ceramics obtained.
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| 5. |
- Fu, Le, et al.
(author)
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Structural integrity and damage of glass-ceramics after He ion irradiation : Insights from ZrO2-SiO2 nanocrystalline glass-ceramics
- 2023
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In: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 43:6, s. 2624-2633
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Journal article (peer-reviewed)abstract
- Developing new radiation-resistant materials and understanding the structural damages caused by radiation are persistent goals of material scientists. Here, we report on the structural integrity and damage to ZrO2-SiO2 nanocrystalline glass-ceramics after radiation with 1.4 MeV He ions at three different fluences: 1.0 x 1016 ions/ cm2 (low), 5.0 x 1016 ions/cm2 (moderate), and 1.0 x 1017 ions/cm2 (high) at 500 degrees C. Grazing incident X-ray diffraction shows the tetragonal-ZrO2 to monoclinic-ZrO2 phase transformation induced by microstrain from the irradiation. The addition of yttrium indicated tetragonal-ZrO2 stabilization effect during irradiation. The irra-diated glass-ceramics show a Raman signal-enhancement effect probably related to the electronic structure changes of the amorphous SiO2 component in the glass-ceramics. The formation of microcracks and lattice de-fects within ZrO2 nanocrystallites is the main structural damage caused by irradiation. There was no observable amorphization of ZrO2 nanocrystallites due to irradiation. No obvious He bubbles were detected, either. The formation of microcracks results in a decrease of in the nanohardness of the glass-ceramics. The results provide fundamental experimental data to understand the structural integrity and damage caused by radiation, which could be useful to design radiation-resistant nanocrystalline glass-ceramics for extremely radioactive environments.
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| 6. |
- Mishukova, Viktoriia, et al.
(author)
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Microsupercapacitors Working at 250 °C
- 2023
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In: Batteries & Supercaps. - : Wiley-VCH Verlagsgesellschaft. - 2566-6223.
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Journal article (peer-reviewed)abstract
- The raised demand for portable electronics in high-temperature environments (>150 °C) stimulates the search for solutions to release the temperature constraints of power supply. All-solid-state microsupercapacitors (MSCs) are envisioned as promising on-chip power supply components, but at present, nearly none of them can work at temperature over 200 °C, mainly restricted by the electrolytes which possess either low thermal stability or incompatible fabrication process with on-chip integration. In this work, we have developed a novel process to fabricate highly thermally stable ionic liquid/ceramic composite electrolytes for on-chip integrated MSCs. Remarkably, the electrolytes enable MSCs with graphene-based electrodes to operate at temperatures as high as 250 °C with a high areal capacitance (~72 mF cm−2 at 5 mV s−1) and good cycling stability (70 % capacitance retention after 1000 cycles at 1.4 mA cm−2).
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| 7. |
- Unosson, Erik, et al.
(author)
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Amorphous Calcium Magnesium Fluoride Phosphate — Novel Material for Mineralization in Preventive Dentistry
- 2023
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In: Applied Sciences. - : MDPI. - 2076-3417. ; 13:10
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Journal article (peer-reviewed)abstract
- This paper describes novel and innovative amorphous calcium magnesium fluoride phosphate (ACMFP) core-shell microparticles that may be applied in preventive dentistry for the prevention of caries and the treatment of dentin hypersensitivity. The particles can be synthesized with varied fluoride content, up to approximately 6 wt%, without any observable differences in morphology or crystallinity. Fluoride release from the particles is correlated to the fluoride content, and the particles are readily converted to fluoride-substituted hydroxyapatite or fluorapatite in a simulated saliva solution. The remineralization and dentin tubule occlusion potential of the particles was evaluated in vitro on acid-etched dentin specimens, and treatment with the ACMFP particles resulted in complete tubule occlusion and the formation of a dense mineralization layer. The acid resistance of the mineralization layer was improved compared to treatment with analogous particles without fluoride inclusion. A cross-sectional evaluation of dentin specimens after treatment revealed the formation of high aspect ratio fluorapatite crystals and poorly crystalline hydroxyapatite, respectively. The particles of the current study provide a single source vehicle of readily available calcium, phosphate, and fluoride ions for the potential remineralization of carious lesions as well as exposed dentin tubules for the reduction of hypersensitivity.
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| 8. |
- Wang, Bohan, et al.
(author)
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Low-temperature and flexible strategy to in-situ fabricate ZrSiO4-based ceramic composites via doping and tuning solid-state reaction
- 2023
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In: JOURNAL OF ADVANCED CERAMICS. - : Tsinghua University Press. - 2226-4108 .- 2227-8508. ; 12:6, s. 1238-1257
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Journal article (peer-reviewed)abstract
- Synthetic zircon (ZrSiO4) ceramics are typically fabricated at elevated temperatures (over 1500 degrees C), which would lead to high manufacturing cost. Meanwhile, reports about preparing ZrSiO4-based ceramic composites via controlling the solid-state reaction between zirconia (ZrO2) and silica (SiO2) are limited. In this work, we proposed a low-temperature strategy to flexibly design and fabricate ZrSiO4-based ceramic composites via doping and tuning the solid-state reaction. Two ceramic composites and ZrSiO4 ceramics were in-situ prepared by reactive fast hot pressing (FHP) at approximately 1250 degrees C based on the proposed strategy, i.e., a ZrSiO4-SiO2 dual-phase composite with bicontinuous interpenetrating and hierarchical microstructures, a ZrSiO4-ZrO2 dual-phase composite with a microstructure of ZrO2 submicron- and nano-particles embedded in a micron ZrSiO4 matrix, and ZrSiO4 ceramics with a small amount of residual ZrO2 nanoparticles. The results showed that the phase compositions, microstructure configurations, mechanical properties, and wear resistance of the materials can be flexibly regulated by the proposed strategy. Hence, ZrSiO4-based ceramic composites with different properties can be easily fabricated based on different application scenarios. These findings would offer useful guidance for researchers to flexibly fabricate ZrSiO4-based ceramic composites at low temperatures and tailor their microstructures and properties through doping and tuning the solid-state reaction.
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| 9. |
- Wang, Maoze, et al.
(author)
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Iontophoresis-Driven Microneedle Arrays Delivering Transgenic Outer Membrane Vesicles in Program that Stimulates Transcutaneous Vaccination for Cancer Immunotherapy
- 2023
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In: SMALL SCIENCE. - : Wiley-VCH Verlagsgesellschaft. - 2688-4046. ; 3
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Journal article (peer-reviewed)abstract
- Transdermal delivery of antigen and chemokine proteins that activates the maturation of skin dendritic cells (DCs) and direct the migration of activated DCs to lymph and spleen is an important alternative to conventional vaccines. However, stratum corneum forms a barrier to skin penetration. The poor cellular uptake of free antigens and chemokines also limits transcutaneous immunization efficacy. In this work, a pair of iontophoresis-driven microneedle patches is constructed, of which, two kinds of outer membrane vesicles (OMVs) derived from Escherichia coli transformed by plasmid encoding gp100 (IPMN-G) and chemokine ligand 21 (IPMN-C) are incorporated within microneedles, respectively. The topical application of IPMN-G and IPMN-C shows the effectiveness of transdermally delivering gp100 and CCL21 secreting vesicles to skin DCs. With iontophoresis as a driving generator, the release and uptake of transgenic OMVs in target cells are significantly enhanced, with transcutaneous immunization initiated. The in vivo applications of IPMN-G and IPMN-C with a 12 h interval retard the progression and prevent the occurrence of tumor spheroids. IPMN-GC is shown as a promising triplatform in engineering transgenic OMV-incorporated microneedles, driven by iontophoresis into a transcutaneous vaccine, providing a noninvasive system for the transdermal delivery of antigen and chemokine proteins for transcutaneous vaccination-meditated immunotherapy.
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| 10. |
- Zhou, Huasi, et al.
(author)
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Effects of N/Si ratio on mechanical properties of amorphous silicon nitride coating
- 2023
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In: Materials Research Express. - : Institute of Physics Publishing (IOPP). - 2053-1591. ; 10:11
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Journal article (peer-reviewed)abstract
- The utilization of silicon nitride coatings has been proposed as an effective method to enhance wear resistance and mitigate the release of metallic ions from biomedical implants. However, the relatively high dissolution rate of low-density coatings remains an obstacle to their implementation. Here, chemical vapour deposition techniques may have advantages over the typically used physical vapour deposition (PVD) methods. Therefore, in this study, silicon nitride coatings were obtained by low-pressure chemical vapor deposition (LPCVD). Since the nitrogen-to-silicon (N/Si) ratio and deposition temperature have been reported as major factors affecting the performance of the coatings, the effects of ammonia (NH3) to dichlorosilane (SiH2Cl2) flow ratio and deposition temperature were systemically investigated in the form of microstructure, mechanical and tribological properties of the coatings. The results revealed that the coatings exhibited a dense structure. As the ammonia flow ratio increased, the surface became smoother, and the hardness and elastic modulus increased and reached the maximum at a flow ratio of 4, giving a hardness of around 27 GPa and an elastic modulus of 290 GPa, respectively. The higher mechanical properties of the coatings deposited at a flow ratio of 4 are attributed to the stronger covalent Si-N bonding, as confirmed by XPS results. However, the coatings deposited at a flow ratio of 2 exhibited the lowest wear rate, at 9.5 x 10-7 mm3 Nm-1, around one-third of the value of the coatings deposited at a flow ratio of 6, likely due to the high silicon content of these coatings. Increasing the temperature resulted in an increased deposition rate, higher hardness and elastic modulus as well as a lower wear rate, likely due to incomplete reactions at lower temperatures. The generally high hardness and low wear rate indicate that the coatings deposited by LPCVD are promising for application in spinal implants.
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